Quick tracer injection for monitoring osmosis membrane integrity

Abstract

A fluorometric monitoring technique can be used to rapidly evaluate the efficiency of an osmosis membrane. In some examples, the technique includes injecting a bolus of fluorescent tracer into a feed stream. The tracer may be introduced for a period of time less than what is required for the tracer to reach an equilibrium concentration in the permeate stream. The feed stream and the permeate stream may be fluorometrically analyzed to determine a flow rate-independent cumulative-time concentration of the fluorescent tracer in the both streams. The efficiency of the osmosis membrane can then be determined based on these flow rate-independent cumulative-time concentrations.

The invention claimed is: 
     
       1. A method for monitoring an osmosis membrane separation process comprising:
 introducing a bolus of fluorescent tracer into a feed stream using a fluorescent tracer pump; 
 contacting an osmosis membrane with the feed stream, thereby generating a permeate stream and a concentrate stream; 
 controlling, by a controller, one or more fluorometers to fluorometrically analyze the feed stream and determining therefrom a measured concentration of the fluorescent tracer in the feed stream over a first period of time corresponding to the bolus; 
 controlling, by the controller, the one or more fluorometers to fluorometrically analyze the permeate stream and determining therefrom a measured concentration of the fluorescent tracer in the permeate stream over a second period of time corresponding to the bolus; 
 determining a flow rate-independent cumulative-time concentration of the fluorescent tracer in the feed stream based on the measured concentration of the fluorescent tracer in the feed stream over the first period of time; 
 determining a flow rate-independent cumulative-time concentration of the fluorescent tracer in the permeate stream based on the measured concentration of the fluorescent tracer in the permeate stream over the second period of time; and 
 determining an efficiency of the osmosis membrane based on comparison of the flow rate-independent cumulative-time concentration of the fluorescent tracer in the feed stream to the flow rate-independent cumulative-time concentration of the fluorescent tracer in the permeate stream. 
 
     
     
       2. The method of  claim 1 , wherein introducing the bolus of fluorescent tracer comprises introducing the fluorescent tracer for a period of time ranging from 1 second to 60 minutes. 
     
     
       3. The method of  claim 1 , wherein introducing the bolus of fluorescent tracer comprises introducing the fluorescent tracer for a period of time ranging from 30 seconds to 5 minutes. 
     
     
       4. The method of  claim 1 , wherein introducing the bolus of fluorescent tracer comprises introducing the fluorescent tracer into the feed stream at a substantially constant rate. 
     
     
       5. The method of  claim 1 , wherein
 fluorometrically analyzing the feed stream over the first period of time corresponding to the bolus comprises fluorometrically analyzing the feed stream for a time within a range from 0 to 60 minutes following initial introduction of the bolus of fluorescent tracer, and 
 fluorometrically analyzing the permeate stream over the second period of time corresponding to the bolus comprises fluorometrically analyzing the permeate stream for a time within a range from 0 to 240 minutes following initial introduction of the bolus of fluorescent tracer. 
 
     
     
       6. The method of  claim 5 , wherein the second period of time is the same as the first period of time. 
     
     
       7. The method of  claim 5 , wherein the second period of time is shifted from the first period of time by at least 1 minute. 
     
     
       8. The method of  claim 1 , wherein determining the flow rate-independent cumulative-time concentration of the fluorescent tracer in the feed stream comprises integrating an area under a curve of the measured concentration of the fluorescent tracer in the feed stream over the first period of time. 
     
     
       9. The method of  claim 1 , wherein determining the flow rate-independent cumulative-time concentration of the fluorescent tracer in the permeate stream comprises integrating an area under a curve of the measured concentration of the fluorescent tracer in the permeate stream over the second period of time. 
     
     
       10. The method of  claim 1 , wherein determining the efficiency of the osmosis membrane based on comparison of the flow rate-independent cumulative-time concentration of the fluorescent tracer in the feed stream to the flow rate-independent cumulative-time concentration of the fluorescent tracer in the permeate stream comprises determining the efficiency according to an equation: 
       
         
           
             
               R 
               = 
               
                 1 
                 - 
                 
                   
                     C 
                     P 
                   
                   
                     C 
                     F 
                   
                 
               
             
           
         
       
       wherein R is the efficiency of the osmosis membrane at rejecting the fluorescent tracer, C P  is the flow rate-independent cumulative-time concentration of the fluorescent tracer in the permeate stream, and C F  is the flow rate-independent cumulative-time concentration of the fluorescent tracer in the feed stream. 
     
     
       11. The method of  claim 1 , wherein the feed stream comprises at least one of a waste water stream and a recycle water stream. 
     
     
       12. The method of  claim 1 , wherein the fluorescent tracer is an inert fluorescent tracer. 
     
     
       13. The method of  claim 1 , wherein the bolus of fluorescent tracer introduced into the feed stream is effective to cause the flow rate-independent cumulative concentration of the fluorescent tracer in the feed stream to range from 1 ppm-sec to 50,000 ppm-sec. 
     
     
       14. A system comprising:
 a fluorescent tracer pump configured to introduce a bolus of fluorescent tracer into a feed stream; 
 a reverse osmosis membrane configured to separate the feed stream into a permeate stream and a concentrate stream; 
 one or more fluorometers configured to fluorometrically analyze the feed stream and the permeate stream; and 
 a controller communicatively coupled to the one or more fluorometers, wherein the controller is configured to:
 control the one or more fluorometers to fluorometrically analyze the feed stream and determine therefrom a measured concentration of the fluorescent tracer in the feed stream over a first period of time corresponding to the bolus; 
 control the one or more fluorometers to fluorometrically analyze the permeate stream and determine therefrom a measured concentration of the fluorescent tracer in the permeate stream over a second period of time corresponding to the bolus; 
 determine a flow rate-independent cumulative-time concentration of the fluorescent tracer in the feed stream based on the measured concentration of the fluorescent tracer in the feed stream over the first period of time; 
 determine a flow rate-independent cumulative-time concentration of the fluorescent tracer in the permeate stream based on the measured concentration of the fluorescent tracer in the permeate stream over the second period of time; and 
 determine an efficiency of the reverse osmosis membrane based on comparison of the flow rate-independent cumulative-time concentration of the fluorescent tracer in the feed stream to the flow rate-independent cumulative-time concentration of the fluorescent tracer in the permeate stream. 
 
 
     
     
       15. The system of  claim 14 , wherein the controller is further communicatively coupled to the fluorescent tracer pump and configured to control the fluorescent tracer pump to introduce the bolus of fluorescent tracer into the feed stream. 
     
     
       16. The system of  claim 15 , wherein the controller is configured to control the fluorescent tracer pump to introduce the bolus of fluorescent tracer into the feed stream for a period of time ranging from 1 second to 60 minutes. 
     
     
       17. The system of  claim 15 , wherein the controller is configured to control the fluorescent tracer pump to introduce the bolus of fluorescent tracer into the feed stream for a period of time ranging from 30 seconds to 5 minutes. 
     
     
       18. The system of  claim 14 , wherein the one or more fluorometers comprise a first fluorometer positioned to fluorometrically analyze the feed stream and a second fluorometer positioned to fluorometrically analyze the permeate stream. 
     
     
       19. The system of  claim 14 , wherein the first period of time is within a range from 0 to 60 minutes following initial introduction of the bolus of fluorescent tracer and the second period of time is within a range from 0 to 240 minutes following initial introduction of the bolus of fluorescent tracer. 
     
     
       20. The system of  claim 19 , wherein the second period of time is the same as the first period of time. 
     
     
       21. The system of  claim 19 , wherein the second period of time is shifted from the first period of time by at least 1 minute. 
     
     
       22. The system of  claim 14 , wherein the controller is configured to:
 determine the flow rate-independent cumulative-time concentration of the fluorescent tracer in the feed stream by at least integrating an area under a curve of the measured concentration of the fluorescent tracer in the feed stream over the first period of time; and 
 determine the flow rate-independent cumulative-time concentration of the fluorescent tracer in the permeate stream by at least integrating an area under a curve of the measured concentration of the fluorescent tracer in the permeate stream over the second period of time. 
 
     
     
       23. The system of  claim 14 , wherein the controller is configured to determine the efficiency of the reverse osmosis membrane based on comparison of the flow rate-independent cumulative-time concentration of the fluorescent tracer in the feed stream to the flow rate-independent cumulative-time concentration of the fluorescent tracer in the permeate stream by at least determining the efficiency according to an equation: 
       
         
           
             
               R 
               = 
               
                 1 
                 - 
                 
                   
                     C 
                     P 
                   
                   
                     C 
                     F 
                   
                 
               
             
           
         
       
       wherein R is the efficiency of the reverse osmosis membrane at rejecting the fluorescent tracer, C P  is the flow rate-independent cumulative-time concentration of the fluorescent tracer in the permeate stream, and C F  is the flow rate-independent cumulative-time concentration of the fluorescent tracer in the feed stream. 
     
     
       24. The system of  claim 15 , wherein the controller is configured to control the fluorescent tracer pump to introduce the bolus of fluorescent tracer into the feed stream effective to cause the flow rate-independent cumulative concentration of the fluorescent tracer in the feed stream to range from 1 ppm-sec to 50,000 ppm-sec.